1. Field of the Invention
The present invention relates to an image reading apparatus which reads an image which is recorded on a transmission original which is such as a photographic film or the like by light which has been transmitted through the transmission original, and an image reading method thereof.
2. Description of the Related Art
In recent years, a technology has become more common in which an image which is recorded on an original such as a photographic film or the like is photoelectrically read by using a photoelectric conversion element such as a CCD or the like and is stored as digital image data, and then image processings such as enlargement and reduction of the image, various corrections, and the like is carried out on the digital image data, and an image is formed on a recording material such as a photographic printing paper or the like by a light beam which is modulated on the basis of the data subjected to image processing.
Generally, in an image reading apparatus, infrared light, which is emitted from a lamp which serves as a light source, is cut off by using an infrared light cutting filter so as to prevent a photographic film from being damaged by the infrared light emitted from the light source.
On the other hand, if the photographic film which is the transmission original is scratched or if dust adheres to the photographic film, when image reading is carried out by the CCD or the like, the scratches and dust significantly affect image data. Then, when an image is formed on the recording material on the basis of the image data, the scratches and dust appear and affect the finish of the image which is formed on the recording material.
In an image reading apparatus, in order to avoid the influence of such scratches or dust on the original, diffused light is irradiated onto the original when an image is read.
In recent years, the demand for high image quality of images formed by a light beam or the like has been growing, and image reading of high precision is becoming necessary in image reading apparatuses. Thus, in an image reading apparatus, pre-scanning, in which an image recorded on an original is read at low resolution, is carried out and image reading conditions are set. Then, fine-scanning, in which an image is read at high resolution on the basis of the image reading conditions set by the pre-scan, is carried out. As a result, image data having high precision can be obtained.
When image reading is carried out with high precision, it is difficult to form image data which is not affected by scratches on the photographic film or dust adhering to the photographic film simply by irradiating diffused light onto an original.
On the other hand, infrared light, which is invisible light, is transmitted without being affected by a visible image recorded on a transmission original such as a photographic film or the like, but if the photographic film is scratched or dust adheres to the photographic film, an amount of transmitted light varies.
In the invention disclosed in Japanese Patent Application Publication (JP-B) No. 6-78991 or the like, when a transmission original such as a photographic film is read, scratches, dust and the like on the transmission original are detected by infrared light and image data read by visible light is corrected so as to obtain appropriate image data which is not affected by scratches or dust on the photographic film.
However, when image reading is carried out with high precision, in addition to scanning for reading R, G and B image data, it is necessary to carry out scanning for reading data of invisible light such as infrared light. As a result, image reading takes a long time, and efficient and rapid image reading is interfered.